The invention relates to a vascular prosthesis implantation device. More particularly, it relates to a dilation catheter associated with a balloon that enables a stent to press on a vascular prosthesis in a blood vessel. The invention will have an application mainly in the implanting of a vascular prosthesis perpendicular to a puncture in a vessel through which the prosthesis is inserted. Particularly advantageously, the invention will apply to bypasses or the closure of vascular access.